Fits a standard (Nominal) post. (3.5" x 3.5" up to 3.85" x 3.85").Economy caps slide down the post 3/4" and are 4.5" x 4.5" at their widest point.10 year guarantee against fading, discoloration and warping!High impact, remarkably sturdy ASA resin. The same material used to in automobiles!Made in the U.S.A.Quick and easy patented SNAP-CAP installation, built right into the cap!Fraction of the cost of comparable wood caps.Contractor and bulk pricing available!These post caps fit standard 4x4 3-1/2" x 3-1/2"(up to 3-3/4" x 3-3/4")pressure treated posts